Method of making thin sheet metal shells



March 2.,- 1943- G. E. BULLOCK 2,312,749

METHOD OF MAKING THIN SHEET METAL SHELLS Filed Aug. 3, 1940 2 Sheets-Sheet l [N VENTOR 6/455 E-BVLLOCK c A Trams/g March 2, 1943. G. E. BULLOCK 2,312,749

METHOD OF MAKING THIN SHEET METAL SHELLS Filed Aug. 3, 1940 2 Sheets-Sheet 2 Y INVENTOR GILES E BULLOCK ATTORN Y Patented Mar. 2, 1943 UNITED STATES PAT NT orries METHOD OF SIlEET IVIETAL I l H i Giles E. Bullock, Rochester, N. Y. Application August 3,1340, Serial No. 350,480 2 Claims. (Cl. 113-51) This invention relates to methods of making deep drawn metallic shells from thin sheet metal stock, and the principal object of the invention is to provide a novel method of forming so that a deep metallic shell having a dome and a collar on top of the dome may be formed with but two continuous drawing operations.

Heretofore the formation of a deep drawn metallic shell from thin sheet stock has always required three or more separate and comparatively short drawing operations in order to prevent the thin stock from tearing during any of the drawing operations. In contrast to this, the present invention, however, embodies not just the use of but two drawing dies which perform consecutive drawing operations, but the invention provides a novel manner of drawing so that but two drawing operations are necessary to cause the thin metal stock to form itself into shape without giving the metal a chance to crystalize or set at any critical point during the drawing operations.

These and other objects and attendant advantages of the invention will become more readily apparent from the detailed description thereof which follows, reference being had to the accompanying drawings in which Figure l is a partial sectional view and front elevation of the die which is used to perform the first drawing operation in my invention.

Figure 2 is a cross section of a blank from which the shell is formed.

Figure 3 shows a cross section of the blank as it appears shortly after the beginning of the first drawing operation.

Figure 4 shows a cross section of the blank as it appears at the end of the first drawing operation.

Figure 5 is a partial sectional view and front elevation of the die which is used to perform the second or final drawing operation in my invention.

Figure 6 is a cross section of the blank during the drawing operation in the die illustrated in Figure 5.

Figure 7 is a cross section of the finished shell.

The die used in performing the first step in my invention illustrated in Figure 1 comprises the die shoe l which is mounted on the bed plate of a suitable drawing press (not shown). The die shoe fixedly carries the die holder 2 and movable above it the punch holder 3 and the blank holder 4. The blank holder is guided in its movement relative to the die in'the die holder by suitable guide pins 5, 5 which are mounted in the die shoe and project above the die holder for the bushings 6, 6 of the blank holder to slide thereon. The punch holder is centrally mounted to slide in the blank holder and is threaded to the ram of the press by means of the stud 1. The bottom of the punch holdeg carries the drawing punch 8 and carried on the underside of the blank holder surrounding the draw punch is the blanking punch 9.

In the die holder is mounted the blanking die l0 which cooperates with the blanking punch 8 to give the blank of sheet stock its proper shape and dimension. Within this blanking die is yieldingly supported the supporting pad I I which cooperates with the bottom face of the blanking punch 9 to yieldingly hold the blank between them while the drawing operation on the blank takes place.

Centrally of the die holder is fixedly mounted the draw punch H which is adapted to have the hollow center of the movable draw punch 8 telescope thereover while the yleldingly supported draw punches l3 and I4, which concentrically surround the fixed draw punch l2, cooperate withthe bottom of the movable draw punch 8 in the formation of the blank in the first drawing operation.

A suitable double action press is used for the operation of the die, and the punch holder 3 and blank holder are so attached and mounted in the press that the operation thereof causes the blank holder 4 to have the blanking punch 9 engage the blank to hold it yleldingly between it and the pad ll while the fixed cutting die 10 operates to trim the blank between the outer cutting edges of the blanking punch and blanking die. After the blank is trimmed a continued downward movement of the blank holder against the yielding resistance of the springs l5 which support the pad ll causes the yieldingly supported drawing punch iii to bulge the center of the blank upwardly into the angularly recessed bottom of the drawing punch 8. Further joint movement of the blanking punch 9 and drawing punch 8 then causes the draw punch l3 to yield on its support which is preferably an air cushion with which it is connected by means of the rods I6. The blank is thereby bulged upwardly until the face of the draw punch l4 engages the underside of the blank to have the bulge completely shaped into the angular recess of .the draw punch 8.

The draw punch 8 is then given an independent additional movement by the press to have the fixed draw punch I2 telescope intothe hollow center of the moving draw punch I while the blank is yieldingly held between the pad ii and the draw punches i3 and H4 at the bottom and the blanking die and the angularly recessed bottom of the draw punch 8 at the top. In this latter operation, a cylindrical, inverted pocket is formed in the blank centrally of the bulge previously formed therein.

The die illustrated in Figure which performs the second and final drawing operation comprises the -die shoe II which fixedly supports the die holder 2i and movably supports and guides the blank holder 22 by means of the guide pins 23 and guide bushings 24.

Centrally of the blank holder is mounted the draw punch 25 which is threaded to the ram of the press by the stud 2i. Carried on the under side of the blank holder is the holding pad 21 which, in the movement of the blank holder, telescopes into the recess 18 of the stationary pad 29 carried by the die holder 2! and engages the top of the blank located therein to yielding- 1y hold the blank in place in the die holder.

Movement of the punch holder by the press after the blank is held in the die holder causes the partially spherically shaped draw punch 30 yieldingly carried by the punch holder to shape the blank into the correspondingly recessed forming member ii. The latter is yieldingly supported by an air cushion (not shown) a by means of the supporting rods 32, 32 so that continued movement of the punch holder causes the female forming member 3! to yield while the blank is drawn from the recess 28 around the draw punch body 33 to form the cylindrical body portion of the shell. Near the end of this forming operation by the draw punch the partially spherically shaped and yieldingly supported draw punch bottom yields to have the fixed center thereof telescope into the cylindrical pocket of the center of the blank so that the end of the movement of the draw punch causes the blanking punch 34 carried in the'center of the draw punch and slightly projecting therefrom to cooperate with the blanking die 35 carried within the die holder II in order to blank out the bottom of the cylindrical pocket in the blank of the shell formed in the first die.

The hollow center of the holding pad 29 is formed by a ring 36 which is yieldingly supported by suitable springs 31, I1 and at the end of the formation of the cylindrical shell the draw punch body, engages over the top of the shoulder 38, which annularly projects from the guano ring 38 so that when the ring yields on its support the edge of the shoulder 88 cooperates with the edge a of the holding pad II to trim the outside of the outwardly flaring bottom edge 0! the shell formed in the die.

From the foregoing it will be apparent that the novel method of forming a deep drawn shell with a dome and a reduced collar at one end from thin sheet stock, comprises the forming of the sheet stock in a continuous forming operation into the blank illustrated in section in Figure 4 by continuously drawing the central portion of the blank upwardly in such a way as to preclude the necessity of annealing thru any stages in the formation of the shell until a substantially inverted cylindrical pocket having the dimensions for the collar of the shell is formed in the center of the blank and is connected with the outer flat portion of the blank by a substantially conically shaped wall.

The blank thus preliminarily formed from the sheet stock is then subjected to a further continuous drawing operation in such a ways: to preclude the necessity of annealing thru any stages in the formation of the shell during which the conical wall is shaped into the dome, the remaining flat portion of the blank is formed into the cylindrical body of the shell, after which the edge of the cylindrical body is trimmed oil at one end of the shell and the center of the.

cup is blanked out at the other end of the shell.

I claim: i

1. The method of forming a deep cylindrical shell having a dome and a collar of reduced diameter on top of said dome from thin sheet stock which consists in drawing a flat sheet blank to form a raised center having a cylindrical pocket and a substantially conical wall intermediate the flat edge portion of the blank and the cylindrical pocket, then forming the intermediate conical wall of the blank into a dome and drawing the flat edge portion of the remainder of the flat portion of the blank into a cylindrical continuation of the dome for the body of the shell in one continuous drawing operation. 1

2. The method of forming an open ended deep cylindrical shell as set forth in claim 1 and trimming the edge of the cylindrical body at one end of the shell and blanking out the center of the cup at the other end of the shell on the completion of the continuous drawing operation of the cylindrical body.

GILES E. BULIDCK. 

